Unless you've been living under a rock, you know that a 20-year-old Mariah Yeater filed suit in San Diego on Halloween claiming she had a sexual encounter with Justin Bieber following his Oct. 25, 2010, concert at Los Angeles' Staples Center that resulted in her becoming pregnant with his child. Bieber vehemently denies that Yeater's 3-month-old son is his (or that he has ever even met her) and has agreed to take a paternity test in the case.

"We are encouraged that Justin Bieber will voluntarily take the paternity test," Yeater's attorneys Lance Rogers and Matt Pare told TMZ earlier this week. For her part, Yeater is busily making the interview rounds, most recently talking about her alleged affair with Bieber to "The Insider."

Bieber's lawyer has said he will "vigorously pursue all available legal remedies to defend and protect Justin against these allegations." But what exactly does that entail? Beyond disproving his paternity in the case, what other legal options are available to Bieber should he decide to pursue them in hopes of warning others that making allegations like these, if they are false, is not a smart move?

According to family law attorney Vikki Ziegler, whose new book " The Premarital Planner: Your Complete Legal Guide to a Perfect Marriage" hits stores in January, if Yeater's accusation that the "Mistletoe" singer fathered her child is proven false, there could be potential legal repercussions for Yeater should Bieber chose to pursue them.

"Celebrities, believe it or not, have legal recourse if someone makes false allegations or defames them in the public by spoken or written word," Ziegler tells MTV News. "Defamation, perjury and paternity fraud … Beiber's legal team may have many options if the paternity test comes back negative alleviating Beiber from any legal responsibility to Yeaters small child."

The least common route would be to pursue a claim of paternity fraud, which according to Ziegler, "Refers to a paternal discrepancy in which a birth mother names a man to be the biological father of a child, particularly for self-interest, when she knows or suspects that he is not the biological father. They are normally not prosecuted but do exist on the books as law in many states."

More common, however, are claims of defamation and perjury.

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While perjury is most often referred to in the context of a trial, it is more broadly defined as willfully giving incomplete, misleading or false testimony while under oath. While there is not expected to be a trial in Bieber's case, Ziegler acknowledges that perjury can extend to statements made in an official capacity, including lawsuits. "Some legal documents are signed 'by swearing to the veracity/truthfulness of the statements under oath,' which means that if someone lies about anything as acknowledged under oath, they could face perjury charges," she says. "Here, Yeater signed a complaint for paternity under oath possibly alleging knowingly false information. That may be a charge that the prosecutors feel is worthy of pursuit."

Ziegler says that while perjury charges are rarely prosecuted, if they are and the individual is convicted, they can face a hefty fine and jail time. "In California, the punishment ranges from fines and probation and no jail time for a first-time offender to up to four years in state prison," she adds.

If testing determines he is not the father, Bieber's main recourse may be to pursue charges of defamation against Yeater. Defamation is any communication or making of a false statements, issued to a third party, about another person that causes harm determined to be libel or slander. Defamation claims must also demonstrate that actual damage has been inflicted as a result of the claim.

"Yeater and her counsel have filed a complaint for paternity, blabbed to all media outlets that Beiber is the father. Check," says Ziegler. Of course, any defamation suit hinges on the allegations at hand being proven false. If Bieber is the father, Ziegler says, "There will be no sustainable defamation suit ever filed."

"The second component of defamation of character, according to most courts and jurisdictions, is the idea of malice on the part of the alleged defamer," Ziegler tells MTV News. "For public figures, and this would include anyone considered a celebrity, they must also prove that the statement was made with 'actual malice,' meaning that Yeater knew her statement that Beiber is the father is actually false – say, if it's true they never met – or it was said reckless disregard to its truth to tarnish his career or reputation."

Speaking more generally, Ziegler tells MTV that a celebrity's reputation is very important to their branding because it is tied closely to sponsorships and endorsement deals that sometimes are valued in the millions. Oftentimes, even the appearance of impropriety on the part of a celebrity can prove detrimental in this regard, which is why an accusation, even if later disproven, can carry so much long-term weight.

"Beiber's reputation is potentially being negatively affected by Yeater's comments based on his celebrity status, his age, the fact that he has a girlfriend and is perceived as a wholesale young man," she says. "Beiber could lose millions while the paternity suit unfolds based on his reputation as a role model for his fans and sponsors."

Any talk of further court action is, of course, hypothetical. If it is proven that Bieber is not the father, he could also chose to walk away without pursuing any action against Yeater. By all accounts, public sentiment most certainly seems to be on the side of the pop star, and with the No. 1 debut of his Christmas album, his reputation does not appear to have yet been impacted by the allegations.

What are your thoughts on Justin Bieber's paternity case? Let us know in the comments.